International Journal of Advanced Robotic Systems
Volume 3 Number 3 Septebmer 2006 |
Stability Enhancement of Mobile Manipulators via Soft Computing, Page 191-198 Abstract: Nowadays the size and dimension of mobile manipulators have been decreased for being usable in various regions. This leads several problems such as danger of instability. Therefore, many researches have been done to overcome the problem of overturning of a mobile manipulator. In this paper, an algorithm for increasing the stability of a mobile manipulator is presented based on the optimization of aperformance index. The path of vehicle and the desired task of the end-effector are predefined. In order to apply the optimal stability criterion, it is more convenient that the manipulator be of a redundant. Considering the interaction between the vehicle and the manipulator and using the genetic algorithm to minimize the stability criterion cooperating with a neural network, the proposed method is a swift algorithm to determine the optimum configuration of the manipulator for real time overturning control of the vehicle. An example for illustrating the significance of the proposed method is presented in a two dimensional configuration.
A New Solution to Map Dynamic Indoor Environments, Page 199-210 Abstract: In this paper, we propose a new algorithm of mapping dynamic indoor environments. Instead of accurate but expensive laser, we employ sonar and camera to map dynamic structured indoor environments. Based on fuzzy-tuned grid-based map (FTGBM), we use two methods: sonar temporal difference (STD) and statistical background subtraction (SBS), to detect and track moving objects when mapping dynamic environments. The former is a consistency-based method realized by monitoring a sequence of temporal lattice maps for a certain number of measurement periods to detect moving objects by using sonars; and the latter is a background subtraction technique which adopts an expectation maximization (EM) learned 3-class mixture of Gaussians to model the nonstationary background relied on sufficient update during mapping process. After finding the moving objects, we propose a fuzzy-tuned integration (FTI) method to incorporate the results of motion detection into the mapping process. The simulation and experiment demonstrate the capabilities of our approach.
Tracking Trajectory Planning of Space Manipulator for Capturing Operation, Page 211-218 Abstract:On-orbit rescuing uncontrolled spinning satellite (USS) using space robot is a great challenge for future space service. This paper mainly present a trajectory planning method of space manipulator that can track, approach and catch the USS in free-floating situation. According to the motion characteristics of USS, we plan a spiral ascending trajectory for space manipulator to approach towards USS in Cartesian space. However, it is difficult to map this trajectory into the joint space and realize feasible motion in joint space because of dynamics singularities and dynamics couple of space robot system. Therefore, we utilize interval algorithm to handle these difficulties. The simulation study verifies that the spiral ascending trajectory can been realized. Moreover, the motion of manipulator is smooth and stable, the disturbance to the base is so limited that the attitude control can compensate it.
Developing a Psychologically Inspired Cognitive Architecture for Robotic Control: The Symbolic and Subsymbolic Robotic Intelligence Control System (SS-RICS), Page 219-222 Abstract: This paper describes the ongoing development of a robotic control architecture that was inspired by computational cognitive architectures from the discipline of cognitive psychology. The robotic control architecture combines symbolic and subsymbolic representations of knowledge into a unified control structure. The architecture is organized as a goal driven, serially executing, production system at the highest symbolic level; and a multiple algorithm, parallel executing, simple collection of algorithms at the lowest subsymbolic level. The goal is to create a system that will progress through the same cognitive developmental milestones as do human infants. Common robotics problems of localization, object recognition, and object permanence are addressed within the specified framework.
An Omnidirectional Mobile Millimeters Size Micro-Robot with Novel Duel-Wheels, Page 223-230 Abstract:A millimeters size omni-directional mobile micro-robot is presented in this paper. A unique duel-wheel structure is designed for no-slip motion during the steering, by turning the slip friction between the wheel and ground into rolling friction. The robot was driven by four electromagnetic micromotors with 2.1mm×2.1mm×1.3mm size. Three of them are for translation and the other one is for rotation. Kinematics model is analyzed to prove the omni-directional mobility. Virtual-Winding Approach (VWA) and PWM-Based Vector- Synthesize Approach(PBVSA) current control methods are presented to satisfy a requirement of higher positioning accuracy. Experimental results demonstrate the feasibility of this concept.
Novel Mobile Robot Simultaneous Loclization and Mapping Using Rao-Blackwellised Particle Filter, Page 231-238 Abstract:This paper presents the novel method of mobile robot simultaneous localization and mapping (SLAM), which is implemented by using the Rao-Blackwellised particle filter (RBPF) for monocular vision-based autonomous robot in unknown indoor environment. The particle filter is combined with unscented Kalman filter (UKF) to extending the path posterior by sampling new poses that integrate the current observation. The landmark position estimation and update is implemented through the unscented transform (UT). Furthermore, the number of resampling steps is determined adaptively, which seriously reduces the particle depletion problem. Monocular CCD camera mounted on the robot tracks the 3D natural point landmarks, which are structured with matching image feature pairs extracted through Scale Invariant Feature Transform (SIFT). The matching for multi-dimension SIFT features which are highly distinctive due to a special descriptor is implemented with a KDTree in the time cost of O(log2N). Experiments on the robot Pioneer3 in our real indoor environment show that our method is of high precision and stability.
Robust Control of Welding Robot For Tracking a Rectangular Welding Line, Page 239-248 Abstract:This paper highlights a welding robot (WR) for its end effector to track a rectangular welding line (RWL). The WR includes five actuators which use a DC motor as a power source. Two controllers are proposed to control the WR’s end effector: a main controller and a servo controller. Firstly, based on WR’s kinematic equations and its feedback errors using backstepping method the main controller is proposed to design the reference-inputs for the WR’s actuators in order that the WR’s end effector tracks the RWL. Secondly, based on the dynamic equation of WR’s actuator, the servo controller is designed using an active disturbance rejection control method. Finally, a control system incorporated with the main controller and the servo controllers make the WR’s end effector robustly track a RWL in the presence of the modeling uncertainty and disturbances during the welding process. In experiment, the main controller which has a function as a master of the control system links to the five servo controllers which have a function as a slave via I2C communication. The effectiveness of the proposed control system is proven through the simulation and experimental results.
Exploration and Navigation for Mobile Robots With Perceptual Limitations, Page 249-258 Abstract: To learn a map of an environment a mobile robot has to explore its workspace using its sensors. Sensors are noisy and have perceptual limitations that must be considered while learning a map. This paper considers a mobile robot with sensor perceptual limitations and introduces a new method for exploring and navigating autonomously in indoor environments. To minimize the risk of collisions as well as to not exceed the range of sensors, we introduce the concept of a travel space as a way to associate costs to grid cells of the map, based on distances to obstacles. During exploration the mobile robot minimizes its movements, including rotations, to reach the nearest unexplored region of the environment, using a dynamic programming algorithm. Once the exploration ends, the travel space is used to form a roadmap, a net of safe roads that the mobile robot can use for navigation. These exploration and navigation method are tested using a simulated and a real mobile robot with promising results.
A Parallel Randomized Path Planner for Robot Navigation, Page 259-266 Abstract:Computation of a collision-free path for a movable object among obstacles is an important problem in the fields of robotics, CIM and AI. Various automatic task level programming systems can be build for robot guidance, teleoperation, assembly and disassembly among others, if a suitable method for motion planning is available. In the basic variation of motion planning, the task is to generate a collision-free path for a movable object among known and static obstacles. Classically the problem was defined for a rigid 6 degrees-of-freedom body as 'the piano mover's problem'. However, the majority of the research has been conducted in the field of robotics, often under the title of path planning. Rapidly-Exploring Random Trees (RRTs) are a recently developed representation on which fast continuous domain path planners can be based. In this work, we have built a parallel path planning system based on RRTs that interleaves planning and execution, first evaluating it in simulation and then applying it to physical robots. Our distributed algorithm, PRRT (parallel RRT), introduces a parallel extension of previous RRT work, the process splitting and parallel cost penalty search with a comment on Real Time Stagnancy reduction, which improves re-planning efficiency, decreases latency involved in finding feasible paths and the quality of generated paths. PRRT is successfully applied to a real-time multi-robot system. In this paper we illustrate how it is possible to implement a parallel version of RRT based motion planner which yields optimal speed up.
Use of Colour and Shape Constraints in Vision-based Valve Operation by Robot, Page 267-274 Abstract: This paper proposes a new strategy for a humanoid robot to approach and operate a valve based on colour and shape constraints. It consists of four stages, namely rough base approaching, fine base approaching, rough hand approaching and fine hand approaching and grasping. The robot estimates the object’s position using its stereo-vision at the first stage. A new visual positioning method is used to determine the valve’s position and pose in the robot’s frame in the second stage. When its hands are near the valve, a visual servoing method is employed to catch the handle of the valve via cameras in end-effectors. The advantages of both eye-in-head and eye-to-hand systems are exploited. Experimental results are presented to verify the effectiveness of the proposed method.
Fluid Model of Sliding Suction Cup of Wall-climbing Robots, Page 275-284 Abstract: The adhering capability, one of the most important performance indexes of wall-climbing robots(WCRs), should be taken into account when a WCR is designed. This paper proposes a novel approach for investigating the adhering characteristics of the sliding suction cup (SSCs) using fluid network theory to enhance the adhering capability of WCRs. The fluid models of the SSCs of two WCRs are developed and equivalent circuits in three cases are presented. The dynamic responses of negative pressure in SSCs are obtained and validated by a set of experiments. It indicated that the theoretical analysis is reasonable and can give some valuable design criteria on the structure parameters of SSCs and control strategies of suction force of SSCs.
|
ARS Web 2006 |